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Failed stellar bombs hint at supernova tipping point

Two peculiar white dwarfs with more oxygen than carbon are like nothing anybody has seen before

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OXYGEN on a planet might be a sign of life, but in two odd white dwarf stars it could indicate a narrow escape from violent death. They could help pin down the point at which stars go supernova.

A group led by Boris Gänsicke at the University of Warwick, UK, found two white dwarfs that hold far more oxygen than carbon, which is unusual. “It’s extreme – these things look very different from any white dwarfs we’ve seen before,” says team member Danny Steeghs.

Creating so much oxygen takes a fiercer nuclear furnace than is needed for a carbon-rich mixture, so the stars that became these white dwarfs must have been hot and massive. Just a little bigger and they would have gone supernova, the team says (Science, ).

These almost-bombs might show more precisely the threshold at which stars explode.

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